This invention relates to a process for the production of fluorobenzophenone derivatives and particularly, 4-fluorobenzophenone derivatives and 4,4'-difluorobenzophenone.
Fluorobenzophenone derivatives, for example 4,4'-difluorobenzophenone are used as materials for producing an aromatic polyketone polymer and 4-fluorobenzophenone derivatives are useful for agricultural chemicals and drugs and intermediates for dyestuffs.
For producing 4,4'-difluorobenzophenone, there have been known, for example, (1) a process of reacting fluorobenzene with carbon tetrachloride in the presence of anhydrous aluminum chloride and then hydrolyzing [J. P. Picard et al, Can. J. Research, 28B, 56 (1950); C.A., 44, 4442a (1950); Funasaka et al, Yukigoseikagaku Kyokaishi, 17, 334 (1959)], (2) a process of effecting Friedel-Crafts' reaction between p-fluorobenzoylchloride and fluorobenzene in the presence of anhydrous aluminum chloride [R. C. Iris et al, Rev. inst. Salubridad y enfermeded. trop., 8, 63 (1947); C.A., 42, 1921a (1948)], (3) a process of oxidizing 2,2'-bis(4-fluorophenyl)-1,1-dichloroethylene with chromic acid [H. L. Bradlow et al, J. Am. Chem. Soc., 69, 662 (1947)] and (4) a process of treating 4,4'-diaminodiphenylmethane with sodium nitrite in anhydrous hydrogen fluoride or in a concentrated aqueous solution of hydrogen fluoride (Japanese Patent Application Kokai No. 54-132,558).
Also, for producing 4-fluorobenzophenone derivatives there have been known, for example, (5) a process of effecting Friedel-Crafts' reaction between a substituted benzoylchloride and fluorobenzene in the presence of anhydrous aluminum chloride [R. D. Dunlop et al, J. Am. Chem. Soc., 55, 1665 (1933); K. C. Joshi et al, J. Indian Chem. Soc., 40, 42 (1963); R. G. Pews et al, J. Am. Chem. Soc., 89, 2392 (1967)] and (6) a process of reacting p-fluorobenzoylchloride with an aromatic hydrocarbon in the presence of anhydrous aluminum chloride [Z. Eckstein et al, Bull. acad. polon. sci., Ser. sci., chim., geol. et geograph., 7, 803 (1959); Chem. Abstr. 54, 21005b (1960)].
However, in case of the processes (1) and (2) fluorobenzene is an expensive material and anhydrous aluminum chloride of more than equimol relative to fluorobenzene is required. Also, the separation of the catalyst is too complicated to reuse it and further, apparatus of anticorrosion are required.
In case of the process (3) fluorobenzene is used as a starting material and a large amount of glacial acetic acid is necessary. Also, since an excess of anhydrous chromic acid is used, a load for treating waste fluid generated to non-pollution becomes heavy.
In case of the process (4) the starting materials are of relatively low costs, while since a large excess of anhydrous and concentrated hydrogen fluoride is used, the recovery of hydrogen fluoride is necessary.
Further, the apparatus for production made of specific materials such as a reaction and recovery vessel of anti-corrosion are required and also, the toxicity of hydrogen fluoride should be taken into consideration.
In case of the processes (5) and (6) fluorobenzene and p-fluorobenzoylchloride are expensive industrially and anhydrous aluminum chloride of more than equimol is necessary. The separation of the catalyst is too complicated to reuse it and also, the load for treating waste fluid generated is heavy. Therefore, conducting these processes in a commercial scale is confronted with various difficulties.